The present invention relates to internal combustion engines and particularly to apparatus and methods for preparing a mixture of a combustible liquid fuel and air for supply to and combustion in an internal combustion engine.
The mixing of a combustible liquid fuel in a predetermined proportion with air is an essential prerequisite to the proper functioning of conventional internal combustion engines. There conventionally exist several different types of apparatus and methods of preparing for and supplying to such engines a combustible mixture of fuel and air, e.g. carbureators and so-called "fuel injection" systems, each of which basically functions to atomize liquid fuel and entrain it in a predetermined ratio with ambient air. With the increases in recent years in the prices of gasoline and other combustible fuels traditionally utilized in the operation of conventional internal combustion engines, a considerable amount of developmental work has been undertaken toward the conservation and more efficient use of such fuels in such engines with a significant degree of such development work being directed toward the improvement of conventional devices and methods for mixing fuel and air.
Since the basic theory of operation of internal combustion engines requires that the fuel and air mixture be suitable for very quick, substantially complete combustion thereof within the combustion chamber or chambers of the engine, the nature of the fuel and air mixture and the size of fuel particles therein has a direct effect upon the efficiency of the combustion performed in the engine and, therefore, upon the fuel consumption of the engine. While the complete vaporization of conventional liquid fuel into its gaseous state in theory best prepares the fuel for quick, complete combustion, the limitations and operational requirements of conventional internal combustion engines, particularly the fixed swept volume of any such engine and the operational requirement of any given engine of a combustion mixture of a predetermined amount of fuel with a predetermined proportionate amount of air, present substantial practical problems in the utilization in a conventional internal combustion engine of a fuel vaporization arrangement. As will be understood, the vaporization of liquid fuel significantly increases the volumetric area occupied by the fuel and accordingly the volumetric area occupied by a mixture of a given amount of the particulate fuel with a given proportionate amount of air is correspondingly increased upon the vaporization of the fuel particles of the mixture. As a result of this inherent increase in volume upon the vaporization of liquid fuel and because of the fixed swept volume of any given internal combustion engine, the operation of the engine on a mixture of vaporized fuel and air necessitates the use of a smaller amount of fuel and air than would be used if the fuel were particulate in nature, thereby to maintain the desired air-to-fuel ratio. As a result, the total vaporization of fuel in a conventional internal combustion engine generally results in undesirably low power output and may additionally increase the fuel use of the engine. Accordingly, it is conventional wisdom that, while the partial vaporization of liquid fuel in the fuel-air mixture utilized in the conventional internal combustion engine will enhance the operation of the engine, the fuel in the mixture should be primarily particulate in nature. As a corollary, it is most desirable that the individual fuel particles of any such mixture be as small in volume as possible to best facilitate quick and complete burning thereof in the engine for the two-fold purpose of achieving the maximum force from the combustion and to minimize the amount of fuel waste from unburned fuel in the mixture, and preferably, some degree of vaporization of the smaller liquid fuel particles in the mixture will occur to enhance this desired result.
As will additionally be understood, the incomplete or inefficient combustion of fuel caused by either the total vaporization of the fuel or the atomization thereof into undesirably large droplets is a significant causative factor in the production in conventional internal combustion engines of undesirably high quantities of environmentally harmful products of combustion such as carbon monoxide, oxides of nitrogen, and hydrocarbons. Because of the magnitude of atmospheric pollution of this sort caused on a nationwide scale by the daily use of automobiles, legislative controls have been enacted to limit the maximum amount of such pollutants which any given automobile engine can exhaust into the atmosphere. To meet these standards, most automobile manufacturers have turned to the utilization of apparatus in the engine exhaust systems thereof particularly arranged to catalytically convert such pollutants into less harmful substances. While such apparatus are genrally effective for this purpose, they have been found to significantly reduce the fuel economy of the engines.
Pursuant to the above-listed basic criteria for efficient fuel consumption in internal combustion engines, virtually all apparatus and methods of preparing a fuel and air mixture therefor operate to entrain in ambient air a particulate mist of the fuel. A considerable degree of the development work toward the improvement of such apparatus and methods has heretofore been directed to maximizing the efficiency of the means and methods by which the liquid fuel is atomized or otherwise converted to a mist to reduce as much as possible the quantity of individual fuel particles in the mist which are of a size too large for substantially complete combustion in the engine. However, it is clear that no such improvement can possibly operate with total and complete efficiency and, therefore, all such systems presently known necessarily will produce at least some quantity of large particles which will not be completely combusted in an internal combustion engine.
It is therefore an object of the present invention to provide a method and apparatus for operation in combination with any conventional means of preparing a mixture of air and particulate fuel which will effectively separate and salvage from the mixture any fuel particles therein which are too large to be quickly and completely combusted in the engine whereby the air and fuel mixture supplied to the engine will be substantially completely combusted therein, providing increased fuel economy and a significant reduction in the production of harmful pollutants as a result of the combustion.